Airfoil lift coefficient varying means



E. R. BREWSTER 2,292,360

AIRFOIL LIFT COEFFICIENT VARYING MEANS Filed July 15, 19:59 2 Shets-Sheet- 1 Aug. 11, 1942.

Aug. 11,- 1942. E. R. BREWSTER 0 AIRFOIL LI FT COEFFICIENT VARYING MEANS Filed July 15, 1939 v 2 Sheets-Sheet 2 Patented Aug. 11, 1942 UNITED STATES PATENT OFFICE AIRFOIL LIFT Edgar 'Roy Brewster, New Plymouth, New Zealand oosrrromu'r VARYING MEANS Application July 15, 1939, Serial No. 284,788

In New Zealand August 4, 1938 4 Claims.

It has previously been proposed to increase I the lift coeflicient of the wings of an aeroplane by drawing the air downwardly through an apertured upper wing surface by means of an extractor mounted in the fuselage of the aeroplane. While such means are effective in removing the boundary layer, it is obvious that "certain disadvantages are entailed principally due to the increase in weight of the extracting unit and the extra space and expense involved, and general I complication of the method.

The above proposal takes advantage of, crembodies a known principle of aero-dynamics, that the maximum lift coefficient of a wing is dependent upon the degree that the air flow may be bent It is not usual at present in landing to employ the engine power at all, but this invention enables a substantial proportion of the power of the engine to be used for supporting the aeroplane during landing manoeuvres, thus enabling the usual method of support derived from the l peller to draw away a substantial portion of the creased by th substantial removal of the boundary layer from the uppersurface of the wings,

the invention may be said to consist in a method of increasing the lift coefficient of the wings of an aeroplane consisting in utilising a portion of the partial .vacuum created by the usual proboundary layer on the upper surface of the wings.

In that aspect of the invention in which variation of the lift co-eflicient is aimed at, the invention may be said to consist in a method of increasing the lift co-efllcient of the wings of an aeroplane consisting in utilising avariable portion of the partial vacuum created by the usual propeller to downwardly bend to the desired degree the air passing over a portion or portions of the upper surface of the wings.

The invention consists in these features and in the features and arrangements and combinations of parts hereinafter referred to and more particularly pointed out in the claims.

In one way of carrying this invention into ef-- feet, the trailing edge of the wing or aerofoil is split or in other words a hinged flap, somewhat akin to the usual landing or braking flap employed at present in air craft is provided, so

forward speed to be partly dispensed with and thereby enabling agreat reduction in landing speeds.

{is aeroplanesare at present constructed, the

power applied by their engines to the air by means of an airscrew cannot be converted into lift until that power has first been converted into speed, from that speed the lift is then gained by the movement of the wings through the air.

At all times when the medium of speed cannot be fully utilised some proportion of the powe available is in enforced idleness.

Only for take-off and for top speed can the full engine power be made use of. When gliding down the force of gravity supplies the forward thrust and the power cannot usually be employed at all.

An air-screw then is used at present solely for forward propulsion except that it is well known that lift can be derived from the slip-stream thrown back from a tractor air-screw.

In that aspect of the invention and in its simplest form in which the lift coefllcient is inthat th propeller creates a strong suction behind this flap when such flap is open.

By providing the propeller or propellers at the rear of the hinged fia-p so as to create the suction behind such flap, the engine is used directly to increase the lifting force when desired and when otherwise not fully occupied. developing forward speed.

The cutting out of any proportion of the disc area of the propeller .by-the opening of the hinged flap reduces the forward thrust of such propeller. Thus, when landing, instead of throttling down being necessary, my method enables the power applied through the propeller to be diverted to another purpose than solely for forward speed, namely supporting the aeroplane.

By my invention an aeroplane pilot may at will use any proportion of the engine power to create forward thrust and any proportion to increase the lift of the wing according to the division ofthe disc area of th propeller, thereby the aeroplane can be sustained in flight at very low speeds, especially in landing.

By means of differential operation of the flaps coupled with a central division'of the Wing the lift on the two halves of the wing may be increased'unequally or the lift may be increased on one halfonly, for the purpose of lateral control and banking when turning.

reached much beyond those practical by other means.

In its simplest form where the suction of the propeller is applied through the wing to a simple perforated upper surface, this invention will be effective, but an improved result may be obtained by the use of a top surface which is con-- structed wherever convenient as a series of small aerofoils so arranged as to be opened or closed when desired.

It will be realised that more than one engine can be used at the trailing edge and the disc area of each propeller likewise divided up into proportions for thrust and lift.

This invention enables the use of the otherwise idle percentage of the available power to develop the lift of a wing and so support the aeroplane during slow flight and slow landing speed, but the invention is also eflicient in removing the boundary layer and emcient in the prevention of thestalling of the wings at high angles of in cidence, while lateral control can satisfactorily be applied by means of this invention.

While the invention will be described with reference to the accompanying purely illustrative drawings, it is to be clearly understood that the drawings are not to be deemed to limit the broad scope of the invention as hereinbefore disclosed in any. manner.

The invention will now, however, be described with reference to the accompanying drawings in which- Figure 1 is a diagrammatic transverse section through a wing of an aeroplane constructed according to the present invention, with the special construction of the low-speed aerofoils and hinged lower wing-surface in closed position,

Figure 2 is a diagrammatic transverse section through such wing with the special construction of the low-speed aerofoils and hinged lower wing surface in open position, and with the propeller indicated by dotted lines,

Figure 3 is a perspective drawing of an aeroplane constructed according tothe present in vention,

Figure 4 is a rear elevation of such aeroplane showing the low-speed aerofoils and hinged lower wing surfaces,

Figure 5 is a plan of the wing employed in the.

construction shown in Figures 3 and 4,

Figure 6 is a diagrammatic vertical section through the wing of an aeroplane, illustrating an arrangement wherein fixed ducts are provided Figure 8 is a diagram illustrating the manner in which the swept disc area of the propeller is divided up by the construction illustrated in Figure 6.

In the construction shown in Figures 1 and 2,-

the wing section consists of a fixed front aerofoil I which may house the fuel tank, a series of pivoted aerofoils 2, a rear fixed aerofoil land a lower hinged wing surface 4.

The aerofoils '2' and hinged lower wing surface 4 are suitably actuable so that when it is desired to fly slowly they. may be moved to the positions shown in Figure 2, in which the propeller I draws the air through the gaps 6 and passage-way I, thus reducing the pressure above the wing and giving an increased lift thereto. At this stage there is of course some lift on the underside of the wing developed by the impact force of the air struck thereby.

The propeller i is of course so located as to be most effective in drawing the air through the passageway I when the lower wing surface is hinged downwardly as shown in Figure 2.

When the wing is in the position shown in Figure 1, the flight is normal.

In the-construction shown in Figures 3 to 5 the wing middle is provided with flxed and hinged aerofoils as in Figures 1 and 2, and a pusher propeller 5 is employed driven byan enginemounted at the rear of the cabin 8 which is slung below the wing middle, two fuselage members 9 being provided projecting rearwardly to support the rudders lll'and II and elevator l2.

The outer portions I3 of the wings are provided with holes 14 and the interior of such outer the full span of the wing.

The aerofoils 2 and the holes or apertures l4 are provided in a selected portion or portions of the upper surface of the wing. By the term selected portion or portions I mean any portion or portions of the upper surface of the wing where there is no direct frontal or substantially frontal impact of air when the aeroplane is in motion.

With the usual wing, when the critical angle is exceeded, a current of air creeps forward from the trailing edge of the wing above such wing and robs the wing of lift and causes stalling.

By the use of my invention, a current is induced to flow down from the front of the wingto the trailing edge, above the wing, and by preventing a forward current of air prevents stall-' It will be realised of course that it is possible to hinge the top surface of the wing and by the use of the power at the rear of the hinged flap, get the same effect as that obtained with the lower surface of the wing split, although most probably to a lesser degree; also if desired both the upper and lower surfaces can be hinged.

Referring to Figure 5, the middle of the wing is provided with an internal transverse partition I! and the lower wing surfaces are independently controlled to permit banking to be obtained by their use and so dispense with ailerons.

The hinged aerofoils 2 and lower wing surfaces I may be spring-loaded so as to automatically come into operation when the speed of the aeroplane drops, or they may be actuated mechanically or manually or by pneumatic, hydraulic or electrical means. I may for instancemploy any suitable adaptation of the known mean'sfor operating the landing or braking flaps in aircraft foreffecting the desired controlling oper ations.

The design may be such that in normal flight they are'slightly open and the degree of opening is variable automatically or as desired.

The aeroplane shown in Figures 4, and 5 may beprovided with auxiliary tractor motors at l9 (Figure 3). s

per surface of thawing between 2| and the trail-,

ing edge.

In Figure 7 the disc area of the propeller is represented by the area of the circle 23, the proportion of the disc area used for forwardflying is represented by the portions 24 and the portion of the disc area used forlift is represented by the cross-hatched portions 25, which are of course variable relatively tothe portions 24, and are variable relatively to each other for banking purposes. I

In Figure 8, the disc area of the propeller is represented by the area of the circle 26, the portions 21 being used for lift and the portion 28 for forward thrust. I

It will of course be obvious that the invention could be applied to a plane in which a plurality of pusher motors are employed.

Ailerons of the usual type may of course be employed.

The invention may of course be applied to a Y plane having more than. one wing, such as a biplane. I I

In operation and having regard to the application of the invention substantially for the purpose of removing the boundary layer, it will be clear that the partial vacuum created by the propeller 20 operates to induce a partial vacuum in the duct l5 through to the interior of the wing 22 thus drawing a portion of the air passing over,

the selectedportion or portions between 2| and the trailing edge downwardly through the wing and out through the duct l5, thus reducing the Without making the statement other than one of assumption and not of fact, it is believed that in-employing my invention with adjustable controls the best forwardspeedwould be attained when the apertures in the selected portion or portions of the upper surfaces -of the wings and the hinged flap 4 are opened lust sufficiently wide to result in the downward rush of air substantially removing the boundary layer.

The invention is mosteffective where, the wing apertures are directly opposite the hinged flap and the propeller. Where the apertures are provided at a-distance alongthe wing from such hingetd' flap and the propeller, the airflow is less It will be realised that-the invention is most readily applicable to aplanehaving a geodetically constructed wing.-

I claim: I I

i. In an airplane having a pusher propeller, the combination comprising a fuselage, a wing on said fuselage having a passage way therethrough extending from' the upper to the lower surface of said wing, a, plurality of hinged aerofoils located in the plane of the top surface of said wing to control the opening of said passage way at the top surface of said wing, a flap hinged at its forward edge at the lower surface of said wing in front of said pusher propeller to control the opening of said passage .way in the lower surface of said wing so that when said flap is open the trailing edge of the wing is split open against the pusher propeller located behind said flap and an inflow of air to said propeller passes through said passage way from the upper surface of said wing thereby increasing the lift coefficient of the wing.' I

2. In anairplane having a pusher propeller, the combination comprising a fuselage, a wing on said fuselage having .a passageway therethrough extending from the upper to the lower surface of saidwing, a plurality of aerofoils located in the plane of the top surface of said wing at the opening of said passage way at the top surface of said wing, a flap hinged at its forward edge at the lower surface of said wing in front of said pusher propeller to control the opening of said passage way in the lower surface of said wing so that when said flap is open the trailing edge of the wing is split open against the pusher propeller located behind said flap and an inflow of air to said propeller passes through said passage way from the upper surface of said wing thereby increasing the lift coefficient of the wins.

3. In an airplane having a pusher propeller, the combination comprising a fuselage, wings on said'fuselage at each side thereof, each of the will-of the operator in order to provide lateral control.

4. In an airplane including a fuselage, the combination of wings on said fuselage and a pusher propeller adjacent the trailing edge of said wings one of said wings having a passageway extending therethrough from top to bottom thereof and flap means mounted on said wing adjacent the trailing edge of said wing under the control of the pilot to vary the eflective disc area of said propellerwhereby the proportion of the air stream created by said propeller passing through said passageway may be varied.

EDGAR nor BREWSTER. 

